package cloudspace.ui.applet.util;

import java.io.IOException;
import java.io.OutputStream;


public class BASE64Encoder extends CharacterEncoder
{

    /** this class encodes three bytes per atom. */
    protected int bytesPerAtom()
    {
        return ( 3 );
    }


    /**
     * this class encodes 57 bytes per line. This results in a maximum of 57/3 *
     * 4 or 76 characters per output line. Not counting the line termination.
     */
    protected int bytesPerLine()
    {
        return ( 57 );
    }

    /** This array maps the characters to their 6 bit values */
    private final static char pem_array[] = {
        // 0 1 2 3 4 5 6 7
        'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', // 0
        'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', // 1
        'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', // 2
        'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', // 3
        'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', // 4
        'o', 'p', 'q', 'r', 's', 't', 'u', 'v', // 5
        'w', 'x', 'y', 'z', '0', '1', '2', '3', // 6
        '4', '5', '6', '7', '8', '9', '+', '/' // 7
    };


    /**
     * encodeAtom - Take three bytes of input and encode it as 4 printable
     * characters. Note that if the length in len is less than three is encodes
     * either one or two '=' signs to indicate padding characters.
     */
    protected void encodeAtom(
        OutputStream outStream,
        byte data[],
        int offset,
        int len ) throws IOException
    {
        byte a, b, c;

        if ( len == 1 )
        {
            a = data[offset];
            b = 0;
            c = 0;
            outStream.write( pem_array[( a >>> 2 ) & 0x3F] );
            outStream.write( pem_array[( ( a << 4 ) & 0x30 )
                + ( ( b >>> 4 ) & 0xf )] );
            outStream.write( '=' );
            outStream.write( '=' );
        }
        else if ( len == 2 )
        {
            a = data[offset];
            b = data[offset + 1];
            c = 0;
            outStream.write( pem_array[( a >>> 2 ) & 0x3F] );
            outStream.write( pem_array[( ( a << 4 ) & 0x30 )
                + ( ( b >>> 4 ) & 0xf )] );
            outStream.write( pem_array[( ( b << 2 ) & 0x3c )
                + ( ( c >>> 6 ) & 0x3 )] );
            outStream.write( '=' );
        }
        else
        {
            a = data[offset];
            b = data[offset + 1];
            c = data[offset + 2];
            outStream.write( pem_array[( a >>> 2 ) & 0x3F] );
            outStream.write( pem_array[( ( a << 4 ) & 0x30 )
                + ( ( b >>> 4 ) & 0xf )] );
            outStream.write( pem_array[( ( b << 2 ) & 0x3c )
                + ( ( c >>> 6 ) & 0x3 )] );
            outStream.write( pem_array[c & 0x3F] );
        }
    }
}